Application of External Prestressing in Steel Beam Reinforcement
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摘要: 某厂房的既有钢梁跨度30 m,因业态调整,新增的幕墙外荷载加大,钢梁的挠度过大不能满足实际的使用要求。传统的加固方式常有如下两种:一种是在钢梁下增设钢柱以减小既有钢梁的跨度,从而减少挠度,但新增的钢柱下的支撑点扩大了原有建筑加固范围;另一种是在既有钢梁下增设型钢,从而加大钢梁的刚度,但随着型钢的加大,整个钢梁的自重也随之增大,显然这样的做法不太经济。同时因本项目施工工期紧、施工条件受限等原因,为在现有的条件下更有效地解决钢梁的挠度问题,针对本项目的特殊性,拟采用体外预应力的方法对既有钢梁进行加固。根据钢梁的跨度及两端支撑情况,预应力钢绞线拟采用双折线线形。通过对体外预应力钢绞线在张力过程中的预应力损失进行分析,得到有效张拉预应力,进而得到有效的预应力钢绞线面积。通过在原有钢梁两端施加张拉力,中间设置转向块,在幕墙安装过程中,对钢梁两端分批进行张拉,从而使外荷载增加的挠度通过预应力钢绞线的张拉进行控制,在外荷载和预应力组合工况下,挠度的变形为零,避免了因为新的荷载增加而带来对既有钢梁挠度的增加。通过体外预应力对既有钢梁的两端进行张拉,在较短的时间内完成了钢梁的加固任务,在有限的时间及其施工操作面上解决了既有钢梁挠度过大的问题,满足了工程的使用要求,且在较短的时间内获得了较大的经济价值,以期为实现低碳、环保、可持续发展的加固模式提供借鉴。Abstract: The existing steel beam described in this paper has a span of 30 m. Due to the industrial adjustment, the external load of the new curtain wall is increased, and the deflection of the steel beam is too large to meet the actual use requirements. There are two traditional reinforcement methods:one is to add steel columns under the steel beams to reduce the span of the existing steel beams, thereby reducing the deflection, but the support points under the new steel columns expand the scope of the original building reinforcement; Another is to add section steel under the existing steel beam, so as to increase the rigidity of the steel beam, but with the increase of section steel, the dead weight of the whole steel beam also increases, which is obviously not economical. At the same time, due to the tight construction period and limited construction conditions of this project, in order to solve the deflection problem of steel beams more effectively under the existing conditions, in view of the particularity of this project, it was proposed to adopt the external prestressing method to strengthen the existing steel beams. Based on the span of the steel beam and the support at both ends, the double folded line type of the prestressed steel strand was adopted. By analyzing the prestress loss of external prestressed steel strand in the process of tension, the effective tensioning prestress was obtained. Then the effective area of prestressed steel strand was obtained. By applying tension at both ends of the original steel beam and setting a steering block in the middle, the two ends of the steel beam were tensioned in batches during the installation of the curtain wall. Thus, the deflection increased by the external load was controlled by the tensioning of the prestressed steel strand. Under the combined working condition of external load and prestress, the deflection deformation was zero, which avoided the increase of deflection of existing steel beams due to the increase of new loads. The two ends of the existing steel beam were tensioned by external prestress, and the reinforcement task of the steel beam was completed in a short time. The problem of excessive deflection of the existing steel beam was solved in the limited time and on the construction operation surface, and the application requirements of the project were met. Thus, it had obtained greater economic value in a relatively short period of time. It is hoped that this paper could provide reference for peers with similar reinforcement conditions and methods, so as to achieve low-carbon, environmental protection, sustainable development of the reinforcement model.
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Key words:
- external prestressing /
- steel beam /
- reinforcement /
- application
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